This invention relates generally to vehicle rearview mirror systems and, more particularly, to vehicle memory mirror systems.
Vehicle memory mirror systems include at least one, and preferably two, electrically operated motors, each of which positions the reflective element with respect to a given axis. By positioning the reflective element about two generally perpendicular axes, the plane of the mirror can be fully positioned. A user-operable switch, such as a joystick or switch pod, is useful to automatically position the mirrors. In a memory mirror system, a monitor device, such as a potentiometer which is coupled to the reflective element, produces a signal indicative of the position of the reflective element with respect to each axis of movement. The signal produced by the monitor device is used in a closed-loop control to allow a controller to reliably position the mirror to particular positions. In this manner, positions of the mirror for different drivers can be stored in memory and retrieved in order to set the mirrors for that driver.
It is generally known in vehicle control systems to provide communication between a vehicle control module and one or more peripheral devices by various communication techniques including digital communications, pulse-width modulation, or other analog communications. It is also generally known to apply such communication techniques between a vehicle control module and control modules in each of the exterior mirror assemblies of the vehicle.
A vehicle typically includes at least two mirrors mounted external of the vehicle, both of which are controlled in the same fashion. In order to avoid duplication of hardware, it is common to provide one user-operable input device in order to control both mirrors. That device typically includes manual buttons for manually positioning the mirror, a selector switch to select one of a driver side or a passenger side mirror, and memory set and recall buttons for operating the memory features of the mirror. The user-operable input device is typically associated with a control device in order to multiplex the switches making up the user-operable device and to communicate with each of the reflective elements. In order to reduce the number of wires between the control device and each of the mirrors, various techniques have been proposed to multiplex the signals. One such technique is to provide a bidirectional digital communication link between each of the outside mirrors and a central vehicle-based control. The central vehicle-based control receives switch inputs from the user-operable device. The central control provides digitally encoded commands to each of the mirrors. A control in each of the mirrors includes a memory element in order to store particular mirror settings entered by one or more vehicle operators, a data processor, and a position sensor for the reflective element. The data processor compares feedback signals from the position sensor in order to position the reflective element to a position stored in the memory element. In this manner, the central vehicle-based control is greatly simplified and does not need to include a memory function. The only requirement of the control vehicle-based control is that it is capable of encoding data signals.
As disclosed in commonly assigned U.S. Pat. No. 5,798,575 issued to Desmond J. O'Farrell, Roger L. Veldman and Kenneth Schofield for a VEHICLE MIRROR DIGITAL NETWORK AND DYNAMICALLY INTERACTIVE MIRROR SYSTEM, the disclosure of which is hereby incorporated herein by reference, vehicles are increasingly being equipped with serial data communication networks. Such networks include a bidirectional serial multiplex communication link over a bus among a plurality of control modules, each containing a microprocessor or microcomputer. While such serial data communication network could be utilized to provide a communication link between the central processor in each of the mirror assemblies, the protocol of the system provides that higher priority messages are communicated without delay while lower priority messages await communication of higher priority messages. Because mirror-positioning messages would be considered lower priority messages, the serial data communication network may often introduce delays in positioning of the reflective elements. Furthermore, the serial data communication networks are relatively complicated with strict protocol definitions and rigorous hardware requirements.
It would be desirable to provide a vehicle memory mirror system which would incorporate the data processing functions, such as memory storage of multiple mirror positions and the like, in a central control remote from at least one of the mirror assemblies while utilizing a low-wire count interface between the central control and the mirror assembly.
It would be desirable to provide two or more speeds of operation of a mirror-positioning system. When the user is manually positioning the mirror, it is desirable to move the mirror at a relatively slow rate in order to avoid overshoot of the desired setting under the control of the operator. However, when the mirror is being repositioned to a fixed setting by the processor, it is desirable for the mirror to move at a faster rate. This is particularly desirable because memory mirrors also include a downward tilt setting which is a permanent setting invoked whenever the vehicle is placed in reverse gear. This rotates the mirrors downwardly in order to provide a back-up aid to the driver who is typically interested in the area around the vehicle, rather than in the distance behind the vehicle, when making difficult parking maneuvers and the like. In order to be useful, it is desirable that the mirrors switch to the downward tilt position immediately upon the vehicle being placed in reverse gear in order to provide immediate assistance to the operator.